Conventional polarization splitters are large in volume, and can not be used in the optical integrated circuits. However, micro optical devices including polarization splitters can be manufactured based on photonic crystals. Up to now, there are two methods, one of which is that a photonic crystal with a TE photonic bandgap and a TM transmission band, or a TM photonic bandgap and a TE transmission band are used to achieve the polarization separation of waves. This kind of polarization splitters can only be used as separate photonic crystal devices, since the transmittance and degree of polarization are poor, and it is difficult to integrate them into other photonic crystal devices. The other is that different relative coupling lengths are designed in order to couple light waves with different polarization states into different waveguides by means of long-distance coupling between waveguides, utilizing the method of the periodic coupling and odd-even state alternation between the waveguides. The polarization splitters obtained by the two methods above, although the volume thereof has been much smaller than that of conventional polarization splitters, still have a relative large volume.